Colour improvement of bi-coloured pears

Reynolds, Johan Schalk (2001-03)

Thesis (MScAgric)--University of Stellenbosch, 2001.


ENGLISH ABSTRACT: Poor colour development in bi-coloured pears is a big concern for the South African deciduous fruit industry, resulting in low Class 1 packouts with huge financial implications. The objective of this study was, therefore, to evaluate manipulation practices to improve colour development. The effect of summer pruning on the colour development of 'Rosemarie' pear fruit was studied over two seasons. Pruning consisted of removing the upright shoots of the current season's growth on the lateral branches. The effect of the time of summer pruning on Class 1 packout percentage and average fruit mass were determined. The percentage blushed fruit (colour grading 1-10) of the trees pruned in November or pruned repeatedly from November to just before harvest were significantly higher than for unpruned control trees or trees pruned at other times. Fruit mass was not affected by summer pruning. A second study was conducted on 'Rosemarie' and 'Forelle' pears and the treatments consisted of non-pinched and pinched, where the bourse shoots were cut back at petal drop. There were no significant differences in fruit colour, fruit size, flesh firmness and total soluble solids after pinching compared to the control. In a third study on 'Rosemarie' and 'Forelle' trees, bourse shoots were removed in combination with defoliation. Spur leaves were removed at different times throughout the season from petal drop towards harvest. Both bourse shoots (Rosemarie), or one bourse shoot (Forelle) per cluster was removed as control, one treatment where no bourse shoots were removed served as a secondary control. Spur leaf removal on 'Rosemarie' and 'Forelle' did not have any significant effect on fruit set, fruit size or total soluble solids. In 'Rosemarie', there was also no significant effect on fruit colour. In 'Forelle', colour improved significantly between unmanipulated branches (control 1) and branches were one bourse shoot was removed (control 2). However, all treatments compared to control 1, improved red colour, indicated by a significant decrease in the hue angle values and an increase in Class 1 packout. A fourth study was conducted on 'Flamingo', 'Forelle' and 'Rosemarie' pears. A number of urea applications were made onto the fruit. Fruit nitrogen content increased with urea sprays. Urea sprays did not affect red colour of 'Flamingo', 'Forelle' and 'Rosemarie' pears. Urea sprays had no effect on the anthocyanin concentration (ug.g") of 'Rosemarie' and 'Flamingo'. However, there was a quadratic relationship between number of urea sprays and anthocyanin concentration of 'Forelle'. There were not significant differences in the chlorophyll a and b concentrations of 'Flamingo' and 'Forelle'. Urea applications significantly increased the chlorophyll a concentration of 'Rosemarie'. In contrast there was no significant difference in the chlorophyll b concentration of 'Rosemarie'. The carotenoid concentration of 'Flamingo' and 'Forelle' was not affected by urea applications. In contrast the carotenoid concentration of 'Rosemarie' increased significantly after the urea applications. Overhead cooling was applied with a micro-irrigation system to 'Rosemarie' pears. The water was applied with pulsed irrigation for a three-week period (24 December 1998 to 14 January 1999) before harvest. The system was activated when internal fruit temperature reached 24°C (day) and 19°C (night), and irrigation continued until internal fruit temperature reached 21°C (day) and 16°C (night). No significant differences were found in colour, soluble solids; fruit size, fimmess or yields. A study was conducted on 'Bon Rouge', 'Red d' Anjou' and 'Forelle' pears to assess the effect of storage period for 6 and 8 weeks at -O.SoC and ripening at 21°C for 1 week on anthocyanins, carotenoids, chlorophyll a and chlorophyll b content. There were no significant differences in the anthocyanin concentration in 'Bon Rouge' after cold storage compared to fruit at harvest, whilst for 'Red d' Anjou' anthocyanin concentration increased significantly after cold storage. Results with 'Forelle' were inconsistent. During ripening anthocyanin of 'Red d' Anjou' did not change, whereas the results for 'Bon Rouge' and 'Forelle' were inconsistent. However, cold storage had no effect on the anthocyanin concentrations of 'Bon Rouge' and 'Forelle'. Cold storage significantly decreased the carotenoid concentrations of 'Bon Rouge', but not in 'Red d' Anjou' and 'Forelle'. The carotenoids of 'Bon Rouge', 'Red d' Anjou' and 'Forelle' decreased significantly more during ripening at 21°C. The chlorophyll concentrations of 'Bon Rouge' decreased significantly during storage at -O.SoC, compared to fruit at harvest, but not in 'Red d' Anjou' and 'Forelle'. During ripening at 21°C chlorophyll a and chlorophyll b decreased significantly in 'Bon Rouge', 'Red d' Anjou' and 'Forelle'. In conclusion it is clear from this study, that although light is important for initial colour development, high December and January temperatures remain the biggest problem in maintaining good red colour at harvest. Other factors, e.g. fertilisation are secondary.

AFRIKAANSE OPSOMMING: Kleurverbetering van twee-kleur pere Onvoldoende kleur ontwikkeling in twee-kleur pere is 'n groot probleem vir die Suid Afrikaanse sagtevrugtebedryf aangesien dit lae Klas l-uitpakke tot gevolg het. Die doel van hierdie studie was dus om manipulasie tegnieke te evalueer om sodoende kleur ontwikkeling te verbeter. Die effek van somersnoei op die kleur ontwikkeling van 'Rosemarie' pere is ondersoek oor twee seisoene. Die snoei het bestaan uit die verwydering van regop lote van die huidige seisoen se groei op laterale takke. Die effek van die tyd van somersnoei op Klas I-uitpakpersentasie en gemiddelde vrugmassa is bepaal. Die persentasie vrugte met 'n blos (kleur gradering 1-10) van die bome wat in November of voortdurend vanaf November tot net voor oes gesomersnoei is, was betekenisvol hoër as die onbehandelde bome of bome wat op ander tye gesnoei was. Vrugmassa was nie beïnvloed deur somersnoei nie. 'n Tweede studie is gedoen op 'Rosemarie' en 'Forelle' bome. Die behandelings was nie-getop of getop, waar die beurslote teruggesny is na blomblaarval. Daar was geen betekenisvolle verskille in vrugkleur, vruggrootte, vrugfermheid en totale oplosbare suikers tussen die getopte en onbehandelde bome se vrugte nie. In 'n derde studie op 'Rosemarie' en 'Forelle' is beurslote verwyder in kombinasie met die verwydering van spoorblare. Spoorblare is verwyder op verskillende tye gedurende die seisoen vanaf blomblaarval tot oes. By 'Rosemarie' (beide beurslote per tros) en by 'Forelle' (een beursloot per tros) is beurslote verwyder om te dien as die kontrole, een behandeling waar geen beurslote verwyder was nie het gedien as die sekondêre kontrole. Spoorblaarverwydering by 'Rosemarie' en by 'Forelle' het geen betekenisvolle effek op vrugset, vruggrootte of totale oplosbare suikers gehad nie. By 'Rosemarie' was daar ook geen betekenisvolle effek op vrugkleur nie. By 'Forelle' is vrugkleur betekenisvol verhoog tussen onbehandelde takke (kontrolel) en takke waar een beursloot verwyder was (kontrole 2). Alle behandelings het egter vrugkleur verhoog in vergelyking met kontrole 1. Dit is waarneembaar in 'n betekenisvolle verlaging in die kleurskakering en 'n verhoging in die Klas l-uitpakke. 'n Vierde studie is uitgevoer op 'Flamingo' en 'Forelle' en 'Rosemarie' pere. 'n Aantal ureumtoedienings is gemaak op die vrugte. Die stikstofinhoud van die vrugte is verhoog met ureumbespuitings. Ureum spuite het nie rooi vrugkleur van 'Flamingo', 'Forelle' of 'Rosemarie' pere beïnvloed nie. Ureumbespuiting het geen effek op die antosianienkonsentrasie (ug.g") van 'Rosemarie' en 'Flamingo' gehad nie. Daar was egter 'n kwadratiese verwantskap tussen die aantal ureumbespuitings en die antosianienkonsentrasie van 'Forelle'. Daar was geen betekenisvolle verskille in die chlorofiel a en b konsentrasies van 'Flamingo' en 'Forelle' nie. Ureumtoedienings het die chlorofiel a konsentrasie van 'Rosemarie' betekenisvol verhoog, daar was egter in teenstelling hiermee geen verskil in die chlorofiel b konsentrasie van 'Rosemarie' nie. Die karotenoiedkonsentrasie van 'Flamingo' en 'Forelle' is nie beïnvloed deur die ureum toedienings nie. In teenstelling hiermee het die karotenoiedkonsentrasie van 'Rosemarie' betekenisvol toegeneem na die ureum toedienings. Oorhoofse verkoeling is toegedien met 'n mikro-besproeiingsstelsel op 'Rosemarie' pere. Die water is toegedien met puls besproeiing vir 'n periode van drie weke (24 Desember 1998 tot 14 Januarie 1999) voor oes. Die stelsel is geaktiveer wanneer die interne vrugtemperatuur 24oe (dag) en 19°e (nag) bereik het, die besproeiing het aangehou totdat die interne vrugtemperatuur 21°e (dag) en 16°e (nag) bereik het. Daar was geen betekenisvolle verskil in kleur, totale oplosbare suikers, vruggrootte, vrugfermheid of opbrengs nie. 'Bon Rouge' 'Red d' Anjou' en 'Forelle' pere is gebruik om die effek van opbergingsperiodes van 6 en 8 weke by -O.5°e en rypwording by 21oe vir 1 week op die antosianiene, karotonoied, chlorofiel a en chlorofiel b konsentrasies te bepaal. Daar was geen betekenisvolle verskille in die antosienien konsentrasie van 'Bon Rouge' na koue opberging nie, terwyl die konsentrasie antosianien by 'Red d' Anjou' betekenisvol toegeneem het na koue opberging. Die resultate by 'Forelle' was nie konstant me. Gedurende rypwording was daar geen verskille in die antosianienkonsentrasie van 'Red d' Anjou' nie, die resultate by 'Bon Rouge' en 'Forelle' was nie konstant nie. Koue opberging het egter geen effek gehad op die antosianienkonsentrasies van 'Bon Rouge'en 'Forelle' nie. Die karonotoied- konsentrasies van 'Bon Rouge', 'Red d' Anjou' en 'Forelle' het betekenisvol meer afgeneem gedurend rypwording by 21°C. Die chlorofielkonsentrasies van 'Bon 'Rouge' het betekenisvol afgeneem gedurende opberging by -O.5°C teenoor die vrugte by oes, maar nie by 'Red d' Anjou' en 'Forelle' nie. Gedurende rypwording by 21°C het die chlorofiel a en chlorofiel b konsentrasies by 'Bon Rouge', Red 'd Anjou' en 'Forelle' betekenisvol afgeneem. Om op te som dit is duidelik uit hierdie studie dat alhoewel lig belangrik is vir vroeë kleurontwikkeling, hoë temperature gedurende Desember en Januarie steeds die grootste faktor is wat finale rooi vrugkleur by oes bepaal. Ander faktore soos bemesting is van sekondêre belang.

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